Inorganic peroxide compounds, such as hydrogen peroxide, solid peroxides, which release hydrogen peroxide by dissolving in water (e.g. sodium perborate and sodium percarbonate perhydrate), have been used as oxidants for disinfection and bleaching for a long time. The oxidation properties of such compounds are strongly dependent on temperature. For example, hydrogen peroxide or perborate in alkaline bleaching liquors show satisfactory, accelerated bleach performance on soiled textiles only at temperatures above 80° C.
At lower temperatures, the efficiency of oxidation of an inorganic peroxide compound can be improved by addition of bleach activators. These bleach activators include N- or O-acyl compounds, e.g. multiple acylated alkylene diamines, especially tetra acetyl ethylene diamine and tetra acetyl glycoril, N-acylated hydantoines, hydrazines, triazoles, hydrotriazines, urazoles, di-keto piperazines, sulfurylamides, and cyanurates, as well as carboxylic acid anhydrides, especially phthalic acid anhydride and substituted maleic acid anhydrides, carboxylic acid esters, especially sodium-acetoxy-benzene sulfonate, sodium-benzoyloxy benzene sulfonate (BOBS), sodium-nonanoyloxy benzene sulfonate (NOBS), sodium-lauroyloxy-benzene sulfonate (LOBS), sodium-isononanoyloxy benzene sulfonate (Iso-NOBS) and acylated sugar derivatives, like pentaglucose. In the presence of such bleach activator substances, the bleach performance of aqueous peroxide solutions can be improved such that similar bleaching results are achieved at a temperature range of 40-50° C., comparable to those of sole peroxide solutions at 95° C. Mixtures of bleach activators may be used as well, which may include both hydrophilic and hydrophobic bleach activators. Mainly, hydrophobic components derivatives of the readily water soluble sodium-phenolsulfonates are used, e.g. nonanoyloxy benzene sulfonate, acetoxy benzene sulfonate or benzoyloxy benzene sulfonate. These hydrophobic compounds are preferably combined with tetra acetyl ethylene diamine. Also, bleach activators based on hydroxy benzoic acids and derivatives thereof show effective bleach performance.
Bleach activators in the form of granules are preferred as bleaching components in combination with substances generating hydrogen peroxide, e.g. sodium perborate or sodium percarbonate for use in laundry, cleaning, and disinfection applications, in textile and fiber treatment preparations, and in the wood, pulp and paper industries. In order to avoid the premature reaction of a bleach activator and peroxide compounds resulting in a loss of bleach performance, a number of processes have been developed to stabilize such systems by granulation, using binders and other additives and to eventually protect the granules by coating.
For example, EP 0 037 026 shows a process for the production of a readily dissoluble granulated activator containing 90% to 98% active matter. The bleach activator in powdered form is homogenously mixed with cellulose or starch ethers in powdered form, followed by spray-on of an aqueous solution of the cellulose or starch ether, followed by granulation processing and a drying step. Because of the gelling of the cellulose and starch ethers in water, causing poor flow properties and low adhesive power, the activator granules according to this reference are less than optimally stable.
In EP 1 447 380 A1, a process for the production of sodium percarbonate is shown. A hydrogen peroxide solution is sprayed onto sodium carbonate while simultaneously drying in an air current. This process yields granules having less than optimal solubility characteristics, especially at low washing temperatures, with resultant, less than optimal bleach performance.
U.S. Pat. No. 5,458,801 discloses a process for producing bleach activators comprising core granules of sodium percarbonate or sodium perborate. The activators are coated with borate, mixed in the presence of water-soluble binders and then granulated. The use of boronic compounds raises toxicological concerns, and therefore these are not preferred components in laundry and cleaning formulations. U.S. Pat. No. 5,458,801 teaches that a granulation process of percarbonate and bleach activators is only possible if the percarbonate is coated with borate.
There is a demand, therefore, for methods and compositions, that combine a bleach activator and bleach material in a form which is easy to produce and highly effective while providing long term shelf stability. The present invention satisfies the demand.